Theft detection and prevention in a power generation system

ABSTRACT

A system for generation of electrical power including an inverter connected to a photovoltaic source including a theft prevention and detection feature. A first memory is permanently attached to the photovoltaic source. The first memory is configured to store a first code. A second memory is attached to the inverter. The second memory configured to store a second code. During manufacture or installation of the system, the first code is stored in the first memory attached to the photovoltaic source. The second code based on the first code is stored in the second memory. Prior to operation of the inverter, the first code is compared to the second code and based on the comparison; the generation of the electrical power is enabled or disabled.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority to U.S.patent application Ser. No. 14/582,363 filed Dec. 24, 2014, now U.S.Pat. No. 9,869,701, which is a continuation of U.S. patent applicationSer. No. 12/788,066 filed May 26, 2010, now U.S. Pat. No. 8,947,194, andentitled “THEFT DETECTION AND PREVENTION IN A POWER GENERATION SYSTEM,”which claims priority to U.S. patent application No. 61/180,940 filedMay 26, 2009, the disclosure of which is incorporated by referenceherein in its entirety.

FIELD AND BACKGROUND 1. Field

The present invention is related to power generation systems, andspecifically to theft detection and prevention of components ofphotovoltaic power generation systems.

2. Related Art

A photovoltaic power generation system incorporates one or morephotovoltaic panels typically mounted on a roof of a building. Aninverter located inside the building connects to the photovoltaicpanels. The power output from the photovoltaic panels is direct current(DC) power. The inverter converts the direct current power toalternating current (AC) power.

The use of photovoltaic panel based power generation systems areattractive from an environmental point of view. However, the cost ofphotovoltaic panels and their relative ease of theft, might limit theiradoption for use in power generation systems. There is therefore a needfor methods and systems for theft detection and prevention ofphotovoltaic panels.

The term “memory” as used herein refers to one or more of read onlymemory (PROM), erasable programmable read only memory (EPROM),electrically erasable programmable read only memory (EEPROM), FLASHmemory, optical memory, e.g. compact disk, switches, random accessmemory (RAM), magnetic memory such as a hard disk or other memory typesknown in the art of

A hash function is a transformation that takes an input and returns afixed-size string or a numeric value, which is called the hash value.The term “hash” as used herein refers to the hash value output of thetransformation.

The term “pairing or paired” as used herein refers to at least two powergeneration system components such as an inverter, photovoltaic panelsand/or electronic modules for example which are “paired” or associatedwith each other. “Pairing” establishes a unique association between forexample an inverter (as opposed to other inverters in a power generationsystem) and a particular set of photovoltaic panels and/or electronicmodules. The “pairing” between power generation components such as aninverter, photovoltaic panel and/or electronic module is typicallyperformed via assignment codes/re-hash of codes, signals or permanentlyattaching additional hardware to each power generation component andeach power generation component being aware of the codes/re-hash ofcodes, signals or permanently attached additional hardware of otherpower generation components as part and parcel of a “pairing” process.The “pairing” process may take place at the time manufacture of powergeneration system components, during installation of a power generationsystem and/or during the operation of the power generation system. Thecodes/re-hash of codes, signals or permanently attached additionalhardware assigned to power generation system components, typicallyestablishes the electrical connections, topographic location, continuedpresence/absence, numbers, types of power generation system componentswithin a power generation system.

The terms “sensing” and “measuring” as used herein are usedinterchangeably.

The term “direct current (DC) power source” as used herein refers to(DC) power source such as batteries, DC motor generator; switch modepower supply (SMPS), photovoltaic panels and/or photovoltaic panelsoperatively attached to a converter module such as a DC to DC converter.

The term “photovoltaic source” as used herein refers to a photovoltaicpanel and/or a photovoltaic panel operatively attached to a convertermodule such as a DC to DC converter.

The term “central unit” as used herein refers to a load such as aninverter or an element such as a control circuit attached directly tothe load or in the immediate vicinity of the load.

BRIEF SUMMARY

According to an aspect of the present invention there is provided amethod for preventing theft of components from a system for generatingelectrical power. The system includes an inverter connected to aphotovoltaic source. A first memory is permanently attached to thephotovoltaic source. A microprocessor and a second memory are attachedto the inverter. A first code is written in the first memory and asecond code is stored in the second memory based on the first code. Thesecond code is preferably either a copy or a hash of the first code. Thewriting of the first code and/or the storing of the second code ispreferably performed during installation of the system. The writing ofthe first code and/or the storing of the second code is optionallyperformed by a remote server attached to the system. After the firstcode is read and stored in the first memory, and the second code is readand stored in the second memory during the electrical power generation,the first code is compared with the second code or its hash. Powerconversion and/or inversion is initialized or continued based on thecomparison of the first code with the second code. The reading of thefirst and second codes and the comparison are preferably performed bythe microprocessor. Alternatively, a remote server operatively attachedto the microprocessor receives the first code and the second code. Theremote server stores in remote storage attached to the remote servereither copies of the first code and the second code or a hash based onthe first code and the second code. Prior to initializing/continuingpower conversion operation of the inverter, the remote server receivesthe first and second codes. The remote server compares the first andsecond codes to the copies/hash previously stored. If the comparison iscorrect, (for instance the codes correspond) then power conversion bythe inverter is allowed. Optionally, the first code or the second codeor portion thereof is generated by a global positioning system modulewhich bases the first code or the second code on the global coordinatesof the photovoltaic source or the inverter.

According to another aspect of the present invention there is provided amethod for preventing theft of a system for generating electrical power.The system includes an inverter connected to a photovoltaic source. Afirst memory is permanently attached to the photovoltaic source. Asecond memory is attached to the inverter. A first code is written inthe first memory and a second code is stored in the second memory basedon the first code. The second code is preferably either a copy or a hashof the first code.

The writing of the first code and/or the storing of the second code ispreferably performed during installation of the system. The first codeand the second code are compared preferably during or prior to theelectrical power generation. The comparison may be performed by aprocessor either a first processor attached to the photovoltaic sourceand configured to address the first memory, a second processor attachedto the inverter configured to address the second memory and/or a remoteserver attached to either the first processor or the second processorover a wide area network. Based on the comparison, either the powerconversion of the inverter is disabled or the electrical power output ofthe photovoltaic source to the inverter is disabled. The first code orthe second code of respective portions thereof may be based on globalcoordinates.

According to another aspect of the present invention there is provided asystem for generation of electrical power including an inverterconnected to a photovoltaic source having a theft prevention anddetection feature. A first memory is permanently attached to thephotovoltaic source. The first memory is configured to store a firstcode. A second memory is attached to the inverter. The second memoryconfigured to store a second code. During manufacture or installation ofthe system, the first code is stored in the first memory attached to thephotovoltaic source. The second code based on the first code is storedin the second memory. Prior to operation of the inverter, the first codeis compared to the second code and based on the comparison. Thegeneration of the electrical power may be enabled or disabled. Thecomparison is performed by a processor: a first processor attached tothe photovoltaic source addressing the first memory, a second processorattached to the inverter addressing the second memory and/or a remoteserver attached to selectably either the first processor or the secondprocessor over a wide area network. The system optionally includes aglobal position module located at the site of the inverter or the siteof the panel The first code or the second code is based on globalcoordinates generated by the global position module.

According to another aspect of the present invention there is provided atheft detection device in a system for generating electrical power, thesystem including a direct current (DC) power source and a loadconnectable to the DC power source with a DC power line. The theftprevention device has an alternating current (AC) source operativelyattached between the load and the DC power source. The AC source ispreferably adapted for superimposing an AC current onto the DC powerline. A receiver located in vicinity of the alternating current (AC)source. An impedance probe operatively attached to the DC power line.The impedance probe is adapted for sensing impedance responsive to theAC current. A rectifier may be adapted to rectify the AC current tosupply power to the impedance probe. A reactive component a capacitorand/or an inductor may be configured to increase impedance sensed by theimpedance probe. The impedance probe may include a voltage probe and acurrent probe, an energy storage device, a memory adapted to store animpedance datum and/or a transmitter which is adapted to transmit theimpedance datum. A potential theft of a component of the system isalerted which is responsive to a change in the impedance greater than apreviously determined threshold.

According to the present invention there is provided a method for theftdetection in a system for generation of electrical power, the systemincluding a DC power line. An alternating current (AC) is applied to theDC power line from an alternating current (AC) source and an impedancecomponent of the system is sensed. The impedance is responsive to theapplied alternating current (AC). An impedance datum proportional to theimpedance is stored with the impedance datum transmitted to a receiver.Electrical charge is stored to power the sensing when the system is notgenerating electrical power. The sensing includes measuring voltage andcurrent of the alternating current (AC) source. A potential theft of acomponent of the system is alerted which is responsive to a change inthe impedance greater than a previously determined threshold or upon notreceiving an expected transmission of the impedance datum.

According to another aspect of the present invention there is provided atheft detection device in a system for generating electrical power. Thesystem includes a direct current (DC) power source with DC outputs. TheDC outputs are connectable to a load with a DC power line. The theftprevention device has an impedance probe connectable to the DC outputsand the DC power line. The impedance probe includes a transmitterconfigured to transmit a probe signal. A receiver module is operativelyattached to the direct current (DC) power source and said load. Thereceiver module includes a receiver configured to receive the probesignal. The probe signal may include data encoded using power linecommunications. A module is operatively attached to the direct current(DC) power source and the load. The module includes a receiverconfigured to receive the probe signal and/or the data. The impedanceprobe may include a voltage probe and a current probe, energy storagedevice and/or memory adapted to store an impedance datum.

According to another aspect of the present invention there is provided amethod for theft detection in a system for generation of electricalpower. The system includes a direct current (DC) power source. Animpedance of the DC power source is measured from which an impedancedatum is stored which is proportional to the impedance. The impedancedatum is transmitted and received. The impedance datum is compared witha previously stored datum and a potential theft of DC power sourceresponsive to the comparison is alerted. The measured impedance mayinclude measured voltage and current of the DC power source. Electricalenergy may be stored for supplying power for the measuring of impedanceand for supplying power for the receiving of impedance datum. Accordingto another aspect of the present invention there is provided a theftdetection device in a distributed electrical power generation systemincluding a direct current (DC) power source connected to an electronicmodule with DC outputs. The DC outputs are connectable to a load with aDC power line. A central impedance probe is connectable to the DC powerline. The central impedance probe includes a impedance sensing moduleadapted for sensing impedance of the DC power source. An electronicmodule may include a bypass switch adapted to present impedance of saidphotovoltaic panel to said central impedance probe.

According to another aspect of the present invention there is provided atheft detection method of theft protection in a distributed electricalpower generation system including a direct current (DC) power sourcewith DC outputs. The DC outputs are connectable to a load with a DCpower line. A central impedance unit is connected to the DC power line.A probe signal is transmitted on the DC power line and impedance issensed responsive to said probe signal. The sensed impedance is comparedto a previously stored impedance value of the direct current (DC) powersource, and an alert may be performed based on the comparison ofimpedance values. The probe signal may be an AC power feed, a power linecommunication signal or a dedicated signal for the impedancemeasurement. The electronic module may be bypassed to present impedanceof the power source, e.g. photovoltaic panel, to the central impedanceprobe.

According to another aspect of the present invention there is provided atheft detection device in a photovoltaic system for generatingelectrical power. The theft detection device has an electronic moduleattached to a photovoltaic source. An image sensor is preferably adaptedfor capturing images of the photovoltaic source. A central controller isadapted to provide a signal to the electronic module. A thermal propertyof the photovoltaic source changes which is responsive to the signal. Aload is preferably connected to the electronic module and the load istypically an inverter. The image sensor is a thermal image sensor. Theelectronic module may include a receiver, direct current (DC) to DCconverter or a DC to alternating current (AC) converter.

According to another aspect of the present invention there is provided amethod for theft detection in a system for generation electrical power,the system including an electronic module attached to a photovoltaicsource. The electronic module is signaled whereupon after receiving thesignaling, the photovoltaic source is reverse biased, thereby causingincreased heat dissipation in the photovoltaic source. Image frames arecaptured of the photovoltaic source and the image frames are analyzedfor thermal changes responsive to the signaling. The presence of thephotovoltaic source is ascertained based on the analyzing of the imageframes and potential theft is alerted of the photovoltaic source basedon the ascertaining. The signaling typically causes the electronicmodule to reverse bias the photovoltaic source.

According to another aspect of the present invention there is provided atheft detection device in a system for generating electrical power, thesystem including an inverter connected to a photovoltaic source, thetheft detection device has a transmitter attached to the photovoltaicsource. The transmitter adapted for transmitting a signal and a receiveris adapted for receiving the signal. The transmitter may be adapted tostore electrical charge.

According to another aspect of the present invention there is provided amethod for theft detection in a system for generation electrical power,the system including an inverter connected to and receiving power from aphotovoltaic source, a transmitter operatively attached to thephotovoltaic source and a receiver. A signal is transmitted from thetransmitter. The signal is monitored and upon an absence of the signalbeing sensed a potential theft of the photovoltaic source is alerted oralarmed.

According to another aspect of the present invention there is provided atheft detection device in a system for generating electrical power, thesystem including an inverter connected to a photovoltaic source. Thetheft prevention device has a transmitter attached to the photovoltaicsource and the transmitter is adapted for transmitting a signal. Areceiver attached to the photovoltaic source is adapted for receivingthe signal and a controller is operatively attached to the receiver andthe transmitter.

According to another aspect of the present invention there is provided amethod for theft detection in a system for generating electrical power,the system including an inverter connected to a photovoltaic source, atransmitter and receiver attached to the photovoltaic source. The signalstrength of the transmitter is measured using the receiver and an objectin vicinity of the photovoltaic source is detected by virtue of changein the measuring. A potential theft of the photovoltaic source isalerted based on the detecting;

According to another aspect of the present invention there is provided atheft detection device in a system for generating electrical power, thesystem including an inverter connected to a photovoltaic source, thetheft detection device has a sensor measuring electric field strength ofthe photovoltaic source and a controller operatively attached to thesensor.

According to another aspect of the present invention there is provided amethod for theft detection in a system for generating electrical power,the system including an inverter connected to a photovoltaic source, asensor operatively attached to the photovoltaic source and a controlleroperatively attached to the sensor. The electric field of thephotovoltaic source is measured using the sensor. The measuring isadapted to indicate a change in threshold of the electric field. Anobject in vicinity of the photovoltaic source is detected by virtue ofchange in threshold of the electric field. Potential theft of thephotovoltaic source is alerted using the controller.

According to another aspect of the present invention there is provided atheft detection device in a system for generating electrical power, thesystem including a photovoltaic string and a load connectable to thephotovoltaic string with a DC power line, the theft prevention devicehas a central control unit operatively attached between the load and thephotovoltaic string. The central control unit is adapted forsuperimposing a control signal and a test signal onto the DC power line.A switch unit operatively attached to the photovoltaic string. Theswitch unit is adapted for receiving the control signal and the testsignal.

According to another aspect of the present invention there is provided amethod for theft detection in a system for generation electrical power,the system including a photovoltaic source and a load connectable to thephotovoltaic source with a DC power line, a central control unitoperatively attached between the load and the photovoltaic source and aswitch unit with a resonant circuit, the switch unit operativelyattached to the photovoltaic source. A first control signal from thecentral control unit is superimposed onto the DC line. The resonantcircuit is connected to the photovoltaic source. The resonant circuit isresponsive to the control signal. A second control signal from thecentral control unit is superimposed onto the DC line. A reflectedsignal responsive to the second superimposing is sensed. The test signalis a time domain reflectometry (TDR) signal or a frequency domainreflectometry (FDR) signal. The sensing may be in terms of sensing phaseshift of the reflected signal, sensing frequency shift of the reflectedsignal and/or sensing amplitude change of the reflected signal.

According to another aspect of the present invention there is provided atheft detection device in a system for generating electrical power. Thedevice includes multiple electronic modules attached to multiplephotovoltaic sources. At least one of the electronic modules is adaptedfor constructing a confirmation signal. A central control unit isoperatively attached to at least one of the electronic modules. Thecentral control unit is adapted for sending a signal to the at least oneelectronic module and for receiving the confirmation signal. Theconfirmation signal typically includes information that the at least oneelectronic module collects from other electronic modules in theimmediate vicinity of the at least one electronic module. The centralcontrol unit may alert of potential theft based on the confirmationsignal.

According to another aspect of the present invention there is provided amethod of theft detection in a system for generation electrical power.The system includes multiple photovoltaic sources, and multipleelectronic modules attached to the photovoltaic sources and a centralcontrol unit. The central control unit is operatively attached to theelectronic modules. A signal is sent from the central control unit to atleast one of the electronic modules. The at least one electronic moduleis adapted for constructing a confirmation signal which is sent to thecentral controller in response. The constructed confirmation signaltypically includes information that the at least one electronic modulecollects from other electronic modules in the immediate vicinity of theat least one electronic module. The confirmation signal is based on orincludes data collected from the electronic modules connected in a meshnetwork. The data is received at the central control unit. Theconfirmation signal may be decoded and the decoded data are comparedwith a look up table stored at the central control unit. Potential theftof one of the photovoltaic sources may be alerted by the central controlunit.

The foregoing and/or other aspects will become apparent from thefollowing detailed description when considered in conjunction with theaccompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1a illustrates an electrical power generation system including atheft prevention feature according to an embodiment of the presentinvention;

FIG. 1b illustrates in more detail a communications module and a memoryof the power generation system of FIG. 1 a;

FIGS. 1c and 1d illustrate a process flow of a method for theftprevention, according to embodiments of the present invention;

FIG. 1e illustrates an electrical power generation system with a theftprevention feature, according to another embodiment of the presentinvention;

FIGS. 1f and 1g illustrate a process flow of a method for theftprevention of in the system of FIG. 1 e;

FIG. 1h illustrates an electrical power generation system, according toyet another embodiment of the present invention;

FIGS. 1i and 1j illustrate a process flow of a method for theftprevention of the electrical power generation system of FIG. 1 h;

FIG. 1k illustrates an electrical power generation system with a theftprevention feature, according to still another embodiment of the presentinvention.

FIGS. 1l and 1m illustrate a process flow of a method for theftprevention of the electrical power generation system of FIG. 1 k;

FIG. 2a shows a power generation system including a theft preventionfeature according to an embodiment of the present invention;

FIG. 2b shows further details of receiver/current source unit andimpedance unit connected as shown in FIG. 2a according to an embodimentof the present invention.

FIG. 2c shows a method for theft detection of a power generation system,according to an aspect of the present invention;

FIG. 2d shows an alternative embodiment of the impedance unit shown inFIG. 2 b;

FIG. 2e shows a power generation system including a theft preventionfeature according to an embodiment of the present invention;

FIG. 2f shows a method for theft detection according to an embodiment ofthe present invention using the power generation system shown in FIG. 2e;

FIG. 2g shows a power generation system including a theft preventionfeature according to an embodiment of the present invention;

FIG. 2h which shows a method of theft protection in a distributedelectrical power generation system according to an embodiment of thepresent invention;

FIG. 3a shows a power generation system including a theft preventionfeature according to an embodiment of the present invention;

FIG. 3b shows a typical topography of the power generation system (shownin FIG. 3a ) including a theft prevention feature according to anembodiment of the present invention;

FIG. 3c shows a method for theft detection according to an embodiment ofthe present invention using the system of FIG. 3a with topography shownin FIG. 3 b;

FIG. 4a shows a power generation system including a theft preventionfeature according to an embodiment of the present invention;

FIG. 4b shows a method for theft prevention using the system shown inFIG. 4a , according to an embodiment of the present invention;

FIG. 4c shows a power generation system including a theft preventionfeature according to an embodiment of the present invention;

FIG. 4d shows a method of theft detection/prevention according to anembodiment of the present invention;

FIG. 5a shows a power generation system including a theft preventionfeature according to an embodiment of the present invention;

FIG. 5b shows a typical cross section of photovoltaic panel according toan embodiment of the present invention;

FIG. 5c shows a plan view photovoltaic panel according to an embodimentof the present invention;

FIG. 5d shows an equivalent capacitor representing a photovoltaic panelaccording to an embodiment of the present invention;

FIG. 5e shows a method for theft detection/prevention according to anembodiment of the present invention;

FIG. 6a shows a power generation system including a theft preventionfeature according to an embodiment of the present invention;

FIG. 6b shows further details of photovoltaic module according to anembodiment of the present invention;

FIG. 6c shows a method for theft detection/prevention using the systemshown in FIG. 6a according to an embodiment of the present invention;

FIG. 7a which shows a power generation system including a theftprevention feature according to an embodiment of the present invention;and

FIG. 7b which shows a method for theft detection/prevention according toan embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below to explain the presentinvention by referring to the figures.

Code Storage

Referring now to the drawings, FIG. 1a illustrates an electrical powergeneration system 157 including a theft prevention feature according toan embodiment of the present invention. System 157 includes one or morephotovoltaic panels 152 connected to an inverter 150 by a direct current(DC) power cable 156. During operation of electrical power generationsystem 157, DC power is produced by photovoltaic panel 152 andtransferred to the input of inverter 150 via DC cable 156. Inverter 150converts the DC power at its input to AC power at inverter 150 output158. A memory module 154 is permanently attached to photovoltaic panel152. A communication module 153 is attached to inverter 150. The term“permanently attached” as used herein refers to a method or device forattachment such that physical removal or attempt thereof, e.g. of memorymodule 154 from photovoltaic panel 152, would likely result in damage,e.g. to module 154 and/or panel 152. Typically, during manufacture ofthe photovoltaic (PV) panel 152 and/or inverter 150, modules 154, 153are “permanently attached” respectively to photovoltaic panel 152 and/orinverter 150. For example, when module 154 is permanently attached tothe photovoltaic panel 152, the operation of photovoltaic panel 152ceases or connections thereof are broken on attempting to remove module154 from photovoltaic panel 152. Any mechanism known in the art for“permanently attaching” may be applied in different embodiments of thepresent invention. One such mechanism for permanently attaching uses athermoset adhesive, e.g. epoxy based resin, and hardener.

Reference is now also made to FIG. 1b , which illustrates in more detail137 communications module 153 and memory module 154 of system 157. Acommunications cable 168 connects memory module 154 to communicationsmodule 153. Power cable 156 which transfers DC power from photovoltaicpanel 152 to the input of inverter 150, is optionally a multi-core cable156/168. At least two wires of the multi-core cable 156/168 preferablyare used for communication cable 168. If a long distance, separatesinverter 150 from photovoltaic panel 154 communication cable 168 ispreferably a twisted pair cable. Alternatively, communications aresuperimposed on DC power line 156, i.e. power line communications.Alternatively, radio frequency wireless communication may be used eithercentrally from inverter to power sources or a mesh network may be used.Communication module 153 attached to inverter 150 preferably includes abus controller 164 (e.g. Cyclone™1C3, i²c bus controller, Altera, 101San Jose Calif. 95134) which controls communications over cable 168. Buscontroller 164 is preferably connected to a microprocessor 160. A memory175, is preferably connected to both bus controller 164 andmicroprocessor 160. Microprocessor 160 preferably outputs a signal 174,which is used to allow/disallow the operation of inverter 150 forconverting DC power to AC power. Memory module 154 which is permanentlyattached to photovoltaic panel 152 includes a memory 159. Memory 159 isconnected to bus controller 164 in communication module 153 bycommunication cable 168. Memory 159 stores a code 1000. Memory 175stores a code 2000.

Reference is now also made to FIGS. 1c and 1d which show a process flowof a method 1700 for theft prevention which illustrates pairing inelectrical power generation system 157, according to an embodiment ofthe present invention. Typically, during manufacture, memory module 154is permanently attached (step 100) to photovoltaic panel 152. In step102, communication module 153 is attached to inverter 150. Althoughsteps 100 and 102 are typically performed during manufacture/assembly ofphotovoltaic panel 152 and/or inverter 150, steps 100 and 102 may beperformed as a retrofit or during installation. In step 103, code 1000is written in memory 159 during manufacture of photovoltaic panel 152 orduring installation of photovoltaic panel 152. Communication module 153reads (step 104) code 1000 using bus controller 164 and microprocessor160. Microprocessor 160 stores (step 105) a copy or hash of code 1000read in step 104 into code 2000 in memory 175. Although, method steps103, 104 and 105 are typically performed during installation ofphotovoltaic panel 152 and inverter 150, steps 103, 104 and 105 may beperformed during manufacture/assembly of photovoltaic panel 152 and/orof inverter 150. Method 1700 continues in FIG. 1d as sub-process 1700(b)performed typical during power generation operation of system 157.Microprocessor 160 reads (step 1200) code 1000 in memory module 154. Instep 1202, microprocessor 160 compares code 1000 with code 2000previously stored in communication module 153 and memory module 175. Indecision box, 1204 if codes 1000 and 2000 are the same or otherwisecorrectly compare then output 174 is set by microprocessor 160 to allowthe power conversion of DC to AC of inverter 150 and anti-theft process1700 continues at step 1200. Otherwise power conversion DC/AC ofinverter 150 is disabled (step 1206) by microprocessor 160 using output174.

Reference is made to FIG. 1e which illustrates another embodiment of thepresent invention, photovoltaic system 147 with a theft preventionfeature. Memory module 154 is permanently attached to photovoltaic panel152 (not shown in FIG. 1e ). Memory module 154 includes memory 159 forstoring code 1000. Memory 159 is connected to bus controller 164 incommunication module 153 by communication cable 168. Communicationmodule 153 is attached to inverter 150 (not shown in FIG. 1e ). Buscontroller 164 is connected to microprocessor 160 and memory 175 forstoring code 2000. A remote server 172 is connected to microprocessor160 by bus 168 or by a dedicated WAN interface (not shown). Remoteserver 172 is connected to a remote storage 172 a. Remote storage 172 apreferably stores copies or hashes of codes 1000 and 2000.Microprocessor 160 has output signal 174, which is activated by remoteserver 172 to allow the operation of inverter 150 to convert DC Power toAC power.

Reference is now also made to FIGS. 1f and 1g which illustrate processflow of a method 7150 for theft prevention of electrical powergeneration system 147 (of FIG. 1e ) according to an embodiment of thepresent invention using. In step 100, memory module 154 is permanentlyattached to photovoltaic panel 152. In step 102 communication module 153is attached to inverter 150. In step 103, code 1000 is written in memory159 during manufacture of photovoltaic panel 152 or during installationof photovoltaic panel 152. Remote server 172 reads (step 1304) code 1000preferably using bus controller 164. Remote server 172 stores (step1305) copies or hashes of code 1000 and code 2000 as code 3000 at remotestorage 172 a. Method steps 103, 1304 and 1305 are typically performedduring installation of photovoltaic panel 152 and inverter 150. Method7150 continues in FIG. 1g as sub-process 7150(b) during which steps1400, 1402, 1404 and 1406 are performed during the power generationoperation of system 147. To protect against theft during operation,remote server 172 reads codes 1000 and 2000 (step 1400). In step 1402,remote server 172 compares the code reads in step 1400 with code 3000 inremote storage 172 a. In step 1404 if codes (1000, 2000) and 3000 arethe same or when code 3000 is a hash of codes 1000 and 2000, and code3000 compares correctly with codes 1000 and 2000, then output 174 ofmicroprocessor 160 activated via remote server 172, allows the powerconversion of DC to AC of inverter 150 and operation continues at step1400. Otherwise, remote server 172 does not allow inverter 150 toconvert DC power to AC power (step 1406).

Reference is made to FIG. 1h of a system 138, according to anotherembodiment of the present invention for theft prevention of photovoltaicsystem 157. Communication module 153 is attached to inverter 150 (notshown) and contains bus controller 164 connected to a microprocessor 160and memory 175 having a code 2000. Connected to bus controller 164 isremote server 172. Remote server 172 is connected to remote storage 172a. Microprocessor 160 has output signal 174, which is activated byremote server 172 to allow the operation of inverter 150 to convert DCPower to AC power. Memory module 154 b permanently attached tophotovoltaic panel 154 b includes memory 159 (e.g. EPROM, EEPROM orFLASH), having a code 1000 and a Global Position System (GPS) module 159a having a code 4000. Code 4000 is based on global coordinates ofphotovoltaic panel 152 during installation of panel 152. Memory 159 andGPS module 159 a are preferably connected to microprocessor 160 by buscontroller 164 in communication module 153 by communication cable 168.

Reference is now also made to FIGS. 1i and 1j which illustrate a processflow of a method 1780 for theft prevention of electrical powergeneration system 138 (FIG. 1h ) according to an embodiment of thepresent invention. In step 100, typically performed during manufactureof electrical power generation system 138, memory module 154 b ispermanently attached to photovoltaic panel 152. In step 102,communication module 153 is attached to inverter 150. In step 103, code1000 is written in memory 159 during manufacture of photovoltaic panel152 or at installation of photovoltaic panel 152. Remote server 172reads (step 1504) code 1000 and code 4000 of GPS module 159 a using buscontroller 164. Remote server 172 stores a copy/hash of codes 1000 and4000 read in step 1504 into code 2000 in memory 175 and in code 3000 ofremote storage 172 a (step 1505). Method steps 103, 1504 and 1505 aretypically performed during installation of photovoltaic panel 152 andinverter 150. Method 1780 continues in FIG. 1j as sub-process 1780(b)performed during power conversion operation of system 138. To protectagainst theft, remote server 172 reads (step 1600) codes 1000, 2000 and4000. In step 1602, remote server 172 compares codes (1000, 2000 and4000) read in step 1600 with code 3000 in remote storage 172 a. At step1604, if codes (1000, 2000, 4000) and 3000 are the same or otherwisecompare correctly, output 174 of microprocessor 160 via remote server172, allows the power conversion of DC to AC of inverter 150 andoperation continues at step 1600. Otherwise remote server 172 does notallow inverter 150 to convert DC power to AC power (step 1406).

Reference is made to FIG. 1k of photovoltaic system 139, anotherembodiment of the present invention for theft prevention. Communicationmodule 153 attached to inverter 150 contains a bus controller 164connected to microprocessor 160 and memory 175, having code 2000.Microprocessor 160 has an output signal 174, which is used to allow theoperation of inverter 150 to convert DC Power to AC power. Memory module154 c permanently attached to photovoltaic panel 152 contains memory159, having a code 1000 and microprocessor 177 with output 176. Memory159 and microprocessor 177 are connected to bus controller 164 incommunication module 153 by communication cable 168.

Reference is now made to FIG. 1l which illustrates sub-processes 1700(b)and 1800(b) being performed in parallel during power conversionoperation after manufacturing/installation is performed according tosub-process 1700(a). Sub-processes 1700(b) and 1800(b) work together inparallel and at the same time to achieve theft detection and preventionof electrical power generation system 139, according to an embodiment ofthe present invention. Sub-process 1700(b) illustrates the use ofmicroprocessor 160 for theft detection and prevention of electricalpower generation system 139. Sub-process 1800(b) illustrates the use ofmicroprocessor 177 for theft detection and prevention of electricalpower generation system 139.

Referring to FIG. 1m , sub-process 1800(b) in step 1200 b microprocessor177 reads code 2000 in communication module 153 by signaling overcommunications bus 168. In step 1202 b, microprocessor 177 compares code2000 with code 1000. If in decision box 1204 b, codes 1000 and 2000 arenot the same, output 176 of microprocessor 177 is used to shut downphotovoltaic panel 152 (step 1206 b). Photovoltaic panel 152 may be shutdown by several mechanisms, by simple bypass using a bypass diode inparallel with photovoltaic panel 152 or by turning off a DC/DCconversion circuit if present in module 154.

A supervisory mechanism is typically provided to remove the pairing inorder to perform re-pairing using different inverters 150 and modules154.

Impedance Measurement

Reference is now made to FIG. 2a which shows a power generation system201 including a theft prevention feature according to an embodiment ofthe present invention. Power generation system 201 has at least onestring 218 of photovoltaic panels 152, an impedance unit 210, a unit212, capacitor C₃, DC power line 216 and load 150. Load 150 ispreferably an inverter. Impedance unit 210 has an impedance probe 200which is connected serially via direct current (DC) line 216 between thepositive output of string 218 and unit 212. When more than one string218 is present each string 218 typically includes its own impedanceprobe 200. Unit 210 maybe optionally incorporated in load 150. Impedanceunit 210 senses impedance of panels 152 with an output connected to atransmitter 202. During daytime operation, impedance unit 210 may bepowered by the current in string 218 or by attaching the probe to asingle photovoltaic panel and receiving power from the photovoltaicpanel in parallel with the string. Impedance unit 210 and/or unit 212may have a charge storage element such as a battery or capacitor fornighttime operation with the charge storage element being charged duringdaytime operation. Transmitter 202 periodically transmits a signalproportional to the measured impedance by impedance probe 200. Unit 212has receiver 204 and an alternating current (AC) source module 206. Unit212 is connected serially between unit 210 and negative output of string218. Unit 210 may be incorporated in a panel 152 or in an electronicmodule 302 (not shown) which is operatively attached/permanentlyattached to a photovoltaic panel 152. Load 150 has a DC input which isserially connected between receiver 204 and alternating current sourcemodule 206 at nodes A and B respectively. Current source module 206 isoptional and may be not needed if unit 210 includes a charge storage. Acapacitor C₃ connects between nodes A and B. Receiver 204 is seriallyconnected between the positive output of string 218 and node A.Alternating current source module 206 is serially connected between nodeB and the negative output of string 218. AC source module 206 isconnected to string of panels 152 and superimposes an AC signal on DCpower lines 216. Impedance probe 200 attached to the string of panels152 measures impedance preferably by independently measuring AC currentand AC voltage along the string of panels.

Reference is now made to FIG. 2b which shows further details of unit 212and impedance unit 210 connected as shown in FIG. 2a according to anembodiment of the present invention. Load 150 connected at nodes A and Bis not shown. Unit 212 has a receiver 204 and AC source module 206. ACsource module 206 includes an AC current source 220 which operates at afrequency typically of 100 KHz. The AC current of source 220 issuperimposed on to DC line 216 via transformer T₂ or any other ACcoupling device. One side of transformer T₂ coil is connected in shuntto a capacitor C₂ and resistor R₁ connected in parallel. One end of R₁is connected to the output of current source 220. The other end of R₁ isconnected to the other output of current source 220 via a DC blockingcapacitor C_(b). The other side of transformer coil T₂ is connected inseries between node B and panels 152 via DC line 216. Receiver 204receives an input of AC present on DC line 216 via one coil oftransformer T₁ connected in series between node A and impedance unit 210via DC line 216. The other coil of transformer T₁ is connected at oneend to the input of a differential amplifier A₁ and the other end of thecoil to the other input of amplifier A₁ via a blocking capacitor C_(b).The output of amplifier A₁ connects into the input of a band pass filter(BPF) 224. The output of band pass filter (BPF) 224 connects into theinput of an analogue to digital (A/D) converter 222. The output ofanalogue to digital (A/D) converter 222 operatively attached toprocessor 226 (with memory).

Impedance unit 210 is connected in series between panels 152 andreceiver 204 via DC line 216. The positive DC output of panels 152 isconnected to one end of an inductor L₁ and one end of a DC blockingcapacitor C_(b). The other end of DC blocking capacitor C_(b) connectsto the input of transmitter 202 as well as to the input of amplifier A₂.The other input of amplifier A₂ connects to one end of capacitor C₁, theanode of a diode D₁ and the other end of inductor L₁. Capacitor C₁ mayserve as a charge storage device to provide power to impedance unit 210during night-time operation. The cathode of D₁ connects the anode ofdiode D₂. The cathode of D₂ connects to the other end of capacitor C₁.The node where the cathode of D₁ connects the anode of diode D₂ providesthe connection to DC line 216. Amplifier A₃ has an input which connectsacross diode D₁. The output of amplifier A₂ may be connected to theinput of an analogue to digital (A/D) converter (not shown) with anoutput connected to a memory storage device (not shown). The output ofamplifier A₃ may be connected to the input of an analogue to digital(A/D) converter (not shown) with an output connected to a memory storagedevice (not shown).

Reference is now also made to FIG. 2c which shows a method 203 for theftdetection of a power generation system 201 which illustrates pairing insystem 201, according to an aspect of the present invention. Analternating current of typically 100 KHz is superimposed or applied(step 205) onto DC line 216 for example via unit 212 and transformer T₂.Optionally, the coil of transformer T₂ connected in parallel with C₂ andR₁ have values selected to operate at a resonance with the seriesinductance of DC line 216 and inductor L₁ located in impedance unit 210.During daylight operation of system 201 direct current flows out frompanels 152 through L₁ and D₁ in impedance unit 210, through receiver104, inverter 150, source 260 and back to the other end of panels 152. Ameasure of the impedance of panels 152 is achieved by sensing (step 207)the current through inductor L₁ via amplifier A₂ and the voltage acrossdiode D₁ via amplifier A₃. A measure of the impedance of panels 152 isachieved by dividing the magnitude of the voltage across diode D₁ by themagnitude of the current through inductor L₁ during sensing (step 207).The measure of the impedance of panels 152 by sensing (step 207) may bestored (step 209) as an impedance datum in a memory (not shown) attachedto amplifier A₂ and A₃ via analogue to digital (A/D) converters (notshown). The stored impedance datum derived by sensing (step 207) mayalso be transmitted (step 211) by transmitter 202 onto power lines 216.Typically during night-time transmitter 202 transmits every 3 minutes.Receiver 204 receives the transmissions of the impedance datum fromtransmitter 202 via one side of transformer T₁. The other side oftransformer T₁ is applied to the input of amplifier A₁. The output ofamplifier A₁ is fed into the input of band-pass filter 224 whichextracts the impedance data sent by transmitter 202. The output ofband-pass filter 224 is then converted to a digital value via analogueto digital (A/D) converter 222 which is optionally stored in processor226 (with memory) operatively attached to the output of analogue todigital (A/D) converter 222. Comparisons (step 213) of stored impedancedatum (step 209) and transmitted impedance datum (step 211) arepreferably made by processor 226. During daylight operation of capacitorC₁ serves as a charge storage device (step 215) to optionally providepower to impedance unit 210 during night-time operation. A potentialtheft of a component of system 201 is alerted (step 217) which isresponsive to a change in the sensed impedance datum comparisons (step213) according to previously determined thresholds. A potential theft isalerted once there is no report from impedance unit 210 sincetransmitter 202 may transmit once in 3 minutes and if a transmission isnot received then the cable may have been cut, when power linecommunication is used.

Reference is now made to FIG. 2d which shows impedance unit 210 a,impedance unit 210 a is an alternative embodiment of impedance unit 210shown in FIG. 2b . Impedance unit 210 a includes a high impedanceinductor L, possibly using resonance to increase impedance and animpedance meter Z. Inductor L is connected in series with impedancemeter Z. Impedance meter Z may have a charge storage element 2100 a suchas a battery or capacitor for nighttime operation which is chargedduring daytime operation. Alternatively, impedance meter Z may bepowered by the method of AC feed. The AC signal that is imposed on theinductor L is rectified when unit 212 includes an AC source used for thepurpose of feeding power to probes 200 and for impedance measurement.Impedance meter Z is typically adapted to transmitimpedance/voltage/current datum via power line communications or via awireless connection.

Reference is now made to FIG. 2e which shows a power generation system201 a including a theft prevention feature which illustrates pairing insystem 201 a according to an embodiment of the present invention. Powergeneration system 201 a has a string 218 a of photovoltaic panels 152,impedance units 210 a, a module 262 and load 150. Load 150 may be adirect current (DC) to alternating current (AC) inverter with an outputwhich connects to a grid voltage (V_(grid)). Impedance units 210 a areconnected serially with panels 152 or may be incorporated as a part of apanel 152 to form string 218 a. Module 262 typically includes a receiver2102 to receive datum transmitted from units 210 a.

During daytime operation module 262 may be powered by the voltage ofstring 218 a, by the grid voltage (V_(grid)) during nighttime operationor module 262 may have a charge storage element 2100 b such as a batteryor capacitor for nighttime operation which is charged during daytimeoperation. During nighttime operation, impedance units 210 a may bepowered by module 262 (providing a typical 12 volts DC current to module210 a) which is powered by the grid voltage (V_(grid)) and/or a chargestorage device 2100 b. During daytime operation, impedance units 210 amay be powered by the current in string 218 a or by taking power from asingle panel. Impedance units 210 a may have a charge storage element2100 a such as a battery or capacitor for nighttime operation which ischarged during daytime operation.

String 218 a is connected serially to the DC input of load 150 viadirect current (DC) lines 216. Module 262 may be incorporated as a partof the circuitry of load 150 or operatively attached to load 150.Impedance units 210 a may sense the impedance of panels 152, the currentflowing in string 218 a or the voltage at a certain point within string218 a depending where impedance unit 210 a is connected in string 218 a.Impedance unit 210 a periodically transmits a datum corresponding to themeasured impedance/DC or AC current/DC or AC voltage datum over powerline communications or via a wireless connection to module 262. Module262 alerts a potential theft of a component of system 201 a which isresponsive to a change in the sensed impedance/current/voltage datumprovided by impedance units 210 a. Not receiving a report is a potentialtheft on its own.

Reference is now made to FIG. 2f which shows a method 219 for theftdetection according to an embodiment of the present invention usingsystem 201 a (shown in FIG. 2e ). Impedance units 210 a preferablymeasures impedance, DC current or DC voltage at various points in string218 a (step 230). Impedance units 210 a preferably have memories tostore measured impedance, DC current or DC voltage as datum (step 232).During daytime operation, impedance units 210 a may be powered by thecurrent in string 218 b. Impedance units 210 a and/or module 262 mayhave a charge storage element (2100 a and 2100 b respectively) such as abattery or capacitor for nighttime operation. The charge storageelements (2100 a and 2100 b respectively) are used to store chargeduring daytime operation (step 233). Impedance units 210 a transmit(step 234) stored measurement datum (step 232) by power linecommunications or via a wireless connection to module 262. Module 262receives the transmitted measurement datum with receiver 2102 andcompares (step 238) the transmitted datum with datum that has beenstored previously in a look table in module 262 as part of a pairingprocess between module 262 and impedance units 210 a. If the comparisonbetween stored datum (step 232) and received datum (step 236) is above acertain pre-defined threshold level, then module 262 may alert apotential theft of a component of system 201 a (step 242), otherwisemeasurement of the impedance, DC current or DC voltage at various pointsin string 218 a (step 230) continues. Not receiving a report in thecentral unit is a potential theft.

Reference is now made to FIG. 2g which shows a power generation system201 b including a theft prevention feature according to an embodiment ofthe present invention. Power generation system 201 b has a string 218 b,photovoltaic panels 152, impedance units 210 a, electronic modules 264,a module 262 and load 150. Load 150 is preferably a direct current (DC)to alternating current (AC) inverter with an output which connects to agrid voltage (V_(grid)). The outputs impedance units 210 a are connectedserially to form a string 218 b. The inputs of impedance units 210 a areconnected to the outputs of electronic modules 264 either in parallel orin series. Impedance unit 210 a may be incorporated as a part of anelectronic module 264. The inputs of electronic modules 264 areconnected to the outputs of panels 152. Module 262 typically includes areceiver 2102 to receive datum transmitted from units 210 a. Electronicmodule 264 additionally may include a bypass 264 a which is connectedserially between the input and output of module 264. Bypass 264 a istypically a single pole switch which is energized to be open circuitwhen module 264 is receiving power from panel 152 or is a capacitor or aseries capacitor and inductor.

During daytime operation module 262 may be powered by the voltage ofstring 218 b, by the grid voltage (V_(grid)) during nighttime operationor module 262 may have a charge storage element 2100 b such as a batteryor capacitor for nighttime operation which is charged during daytimeoperation. During nighttime operation impedance units 210 a may bepowered by module 262 (providing a typical 12 volts DC current) which isbeing powered by the grid voltage (V_(grid)) and/or a charge storagedevice 2100 b. During daytime operation, impedance units 210 a may bepowered by the voltage of module 264 or impedance units 210 a may have acharge storage element 2100 a such as a battery or capacitor fornighttime operation which is charged during daytime operation. There isan additional option for day and/or night operation for 210 a wheremodule 262 sends an AC signal that is rectified by 210 a on someimpedance (e.g. inductor in resonance) to produce DC.

String 218 b is connected serially to the DC input of load 150 viadirect current (DC) lines 216. Module 262 maybe optionally incorporatedas a part of the circuitry of load 150 or operatively attached to load150. Impedance units 210 a preferably measures the impedance of modules264, the current flowing in string 218 b or the voltage at a certainpoint within string 218 b depending where an impedance unit 210 a isconnected in string 218 b or the voltage output of a module 264.Impedance unit 210 a periodically transmits datum corresponding to themeasured impedance/DC current/DC voltage over power line communicationsor via a wireless connection to module 262. Module 262 includes areceiver 2102 to receive datum from module 210 a. Module 262 alerts apotential theft of a component of system 201 a which is responsive to achange in the sensed impedance/current/voltage datum provided byimpedance units 210 a. Again, theft can be detected by not getting areport from the impedance unit 210 a whether or not impedance unit 210 ais incorporated within modules 264.

Impedance measurement may be performed by impedance unit 210 a alone orby using central impedance probe 210 b located in external AC source262, the latter method being appropriate for the case of simple panelswith or without DC module 264. Impedance probe is attached tomicroprocessor 21 which has ports for analogue to digital/digital toanalogue conversion an on board memory.

The impedance that is measured by impedance unit 210 a is actually thesum of impedances reflected by all other impedance units 210 a.Reference is now made to to FIG. 2d as an example of a circuit which maybe included in impedance unit 210 a. Impedance unit 210 a may be part ofDC module 264 and has the output capacitance of the DC module 264 and aseries inductor (a regular inductor L or in resonance in order toincrease its impedance. Another example is that impedance unit 210 abehaves as a capacitor (either as part of DC module 264 or separately)and the impedance measured is the impedance of the capacitor.

According to a feature of the present invention is the ability to sensethat photovoltaic panel 152 is no longer connected to DC module 264, incase that only photovoltaic panel 152 is being stolen. During the day itis straightforward to detect a DC input from panel 152. During thenight, when panel 152 does not output DC, DC module 264 can measure thepanel capacitance or try to impose a voltage and sense whether panel 152draws current at some point (which is its diode voltage).

According to another feature of the present invention, where a panel 152is attached to a module 264 and a panel 152 is stolen at night forinstance by detaching from DC module 264; it is possible to configuremodule 264 to passively present the impedance of panel 152 by use ofbypass 264 a so that such a theft may be detected.

Reference is now made FIG. 2h which shows a method 261 c of theftprotection in a distributed electrical power generation system 201 b,according to an aspects of the present invention. Central impedanceprobe 210 b is connected to DC line 216 (step 263). Probe 210 b thentransmits (step 265) a probe signal onto DC line 216, the probe signalmay be an AC feed or a DC power line communication signal. Transmit step265 is controlled and performed using microprocessor 21. Probe 210 bthen senses (step 267) the impedance of string 218 b as a result ofapplying the probe signal. The sensed impedance in step 267 may then becompared (step 269) with a previously stored impedance value stored inthe memory of microprocessor 21. The comparison may be to subtract thesensed impedance in step 267 from the previously stored impedance valuestored in the memory of microprocessor 21 to produce a difference value.In decision box 271, the difference value may then may be above or belowa certain threshold value, in which case an alert of theft is made (step273), otherwise transmitting of the probe signal continues with step265.

When bypass 264 a is a single pole switch (magnetic reed relay forexample); during the night, when panel 152 does not output DC, thesingle pole switch is normally closed and the panel 152 impedance isbypassed from the input of module 264 to the output of module 264.Typically if module 264 is a power converter circuit, the main switchesin the power converter circuit are open circuit at night, so that theshunt impedance of the output and input of module 264 does not affectthe measurement (step 267) of the panel 152 impedance by probe 210 b(via bypass 264 a). During daytime operation the single pole switch 264a is activated to be open circuit. Another preferable implementation forbypass 264 a, is to make bypass 264 a a fixed bypass between the inputand output of the module 264, were the fixed bypass 264 a reflects panel152 impedance to the output of module 264 but will not interfere withthe way module 264 works. The fixed bypass 264 a may be a seriescapacitor between the input and output of module 264 or a seriescapacitor and inductor between the input and output of module 264 whichmay be operated at resonance.

According to an aspect of the present invention there is provided amethod which relies on impedance measurement performed by a central unit(load/inverter) by sending a signal and measuring voltage/current. Inone example, the signal is a dedicated measurement signal. In this case,impedance/capacitance of panels 152 without any additional circuitry maybe sensed. In another example, the signal is an AC feed for powermodules 264 (during the night or day). In another example, the signal isa power-line-communication that may be used for other purposes (such ascommand and control, monitoring etc.). The additional circuitry, e.g.power modules 264 may reflect an impedance or output capacitance tomeasure. Alternatively, the impedance of a series inductor (e.g.regular, resonance, switched resonance) of DC module 264 is measured bycommand and control from the central unit).

Reference is now made again to FIG. 2f which shows a method 219 fortheft detection according to an embodiment of the present inventionusing system 201 b shown in FIG. 2g . Impedance units 210 a preferablymeasures impedance, DC current or DC voltage at various points in string218 b (step 230). Impedance units 210 a preferably have memories tostore measured impedance, DC or AC current or DC or AC voltage as datum(step 232). During daytime operation, impedance units 210 a may bepowered by the output voltages of modules 264 or impedance units 210 aand module 262 may optionally have a charge storage element 2100 b suchas a battery or capacitor which is used during nighttime operation. Thecharge storage elements (2100 a and 2100 b) are used to store chargeduring daytime operation (step 233). Impedance units 210 a transmit themeasurement datum (step 234) by power line communications or via awireless connection to module 262. Module 262 receives the transmittedmeasurement datum with receiver 2102 and compares (step 238) thetransmitted datum with datum that has been stored previously in a looktable in module 262 as part of a process between module 262 andimpedance units 210 a. If the comparison of datum is above a certainpre-defined level module 262 alerts a potential theft of a component ofsystem 201 a (step 242), otherwise measurement of the impedance, DCcurrent or DC voltage at various points in string 218 a (step 230)continues.

Thermal Camera

Infrared (IR) radiation or heat radiation is herein defined aselectromagnetic radiation whose wavelength is longer than that ofvisible light (400-700 nm), but shorter than that of terahertz radiation(100 μm-1 mm) and microwaves.

Reference is now made to FIG. 3a which shows a power generation system301 including a theft prevention feature according to an embodiment ofthe present invention. An electronic module 302 is operatively attachedto a photovoltaic panel 152. Electronic module 302 may perform directcurrent to direct current (DC/DC) conversion or DC to alternatingcurrent (AC) inverter and according to an embodiment of the presentinvention is capable of reverse biasing a panel 152. Multiple panels 152are connected in series to form a string 304. Load 150 may be a directcurrent (DC) to alternating current (AC) inverter. A central controlunit 300 preferably located in the vicinity of load 150 is operativelyconnected to load 150 and electronic module 302. Central control unit300 optionally provides a signal to electronic module 302 as well asbeing connected to a camera 306 (not shown). The signal from centralcontroller 300 to electronic module 302 may be conveyed over the powerlines connecting load 150 to string 304 or via a wireless connectionbetween controller 300 and module 302.

Reference is now made to FIG. 3b which shows a typical topography 310 ofpower generation system 301 (shown in FIG. 3a ) including a theftprevention feature according to an embodiment of the present invention.Topography 310 includes multiple panels 152 with modules 302 (not shown)which are connected to load 150 and controller 300. A camera 306 islocated in the vicinity of controller 300 and load 150 which are locatedin a building 308. Camera 306 is preferably a thermal imaging camera.The field of view of camera 306 preferably captures images of panels152. The captured images of panels 152 by camera 306 are preferably sentto controller 300 for analysis via power/signal line 309 or via wirelesscommunications.

Reference is now also made to FIG. 3c which shows a method 311 for theftdetection according to an embodiment of the present invention usingsystem 301 with topography 310. During theft detection a signal is sentfrom central unit 300 to an electronic module 302 (step 303). The signalfrom unit 300 to electronic module 302 may be conveyed over the powerlines connecting load 150 to string 304 or via a wireless connectionbetween unit 300 and module 302. Typically the signal sent from unit 300reverse biases panel 152 via module 302 (step 305) for a period of timewhich causes a noticeable rise in panel 152 temperature. After reversebiasing panels 152 (step 305) using module 302, image frames of panels152 are captured using camera 306 (step 307). Unit 300 then analyzes(step 309) the image frames of panels 152 captured by camera 306 (step307). Analyzing the captured image frames preferably means monitoringthe effects of reverse biasing panels 152 or alternatively monitoringthe thermal effects of normal current flow produced during daylightoperation of panels 152 without the use of the signal sent from unit300. Reverse biasing panels using the signal from unit 300 has theeffect of heating up panels 152 thereby altering the infraredradiation/heat radiation of panels 152. The presence of panels 152 isascertained (step 311) by virtue of the infrared radiation changeanalyzed by unit 300 in captured image frames, after a signal from unit300 is applied to a panel 152 via module 302. The alerting of apotential theft (step 313) is therefore achieved by the absence of panel152 not providing a thermal change as a result of applying a signal to apanel 152 via module 302.

Wireless Communications

Reference is now made to FIG. 4a which shows a power generation system401 including a theft prevention feature according to an embodiment ofthe present invention. Photovoltaic panels 152 have transmitters 402operatively attached thereto. Transmitter 402 preferably has a chargestorage device 406 used to power transmitter 402 during the nighttime.The charge storage device 406 of transmitter 402 is charged duringnormal daylight by electricity generated by irradiation of panels 152.Multiple panels 152 are connected in series to a load 150. Load 150 ispreferably a direct current (DC) to alternating current (AC) inverter.Attached to and in the vicinity of load 150 is a receiver 404. Receiver404 receives signals from transmitters 402. Receiver 401 may be composedof an array of receivers/repeaters spread in the solar fieldinstallations which eventually send all received information to inverter150.

Reference is now also made to FIG. 4b which shows a method 403 for theftprevention using system 401, the method 403 is according to anembodiment of the present invention. Transmitters 402 operativelyattached to panels 152 transmit signals (step 405). The transmittedsignals of transmitters 402 are preferably transmitted each on differentfrequencies. The different frequencies that transmitters 402 transmitallow for the unique identification of a particular panel 152. Thetransmitted signals of transmitters 402 are monitored (step 407) byreceiver 404. The monitoring (step 407) by receiver 404 preferablyallows for differentiation and identification of which transmitter 402is transmitting. The absence of a signal from a transmitter ispreferably sensed (step 409) by receiver 404. Receiver 404 preferablyalerts the situation a theft by virtue of an absence of a receivedsignal or signals from transmitters 402.

In an additional method, transmitter 402 sends a signal only upon theft(detected by either specific sensors like accelerometers or bydisconnection from the cable which cuts off signaling or DC feeding frominverter 150.

In an additional implementation, transmitter 402 is passive and containsonly a resonance circuit (in series/parallel) and an antenna. Inverter150 sends an AC signal via the cable that is transmitted passively bythe antenna of 402 and is amplified by the resonance circuit of 402. Anadvantage is that there is no need to feed anything during the night,besides sending a signal on the cable.

Another variant of this method is where photovoltaic panels include amodule with a resonance circuit in a different frequency band such thatload 150 sends all the relevant frequencies (e.g. a frequency sweep) andreceiver 402 senses occurrence of frequency dips, a dip is a specificindication of a stolen module. It gives both identification andadditional accuracy (since the received strength signal is not summedover all modules).

Reference is now made to FIG. 4c which shows a power generation system405 including a theft prevention feature according to an embodiment ofthe present invention. Multiple photovoltaic panels 152 are connected inseries to form a string. The string of photovoltaic panels 152 areconnected across a load 150. Load 150 is preferably a direct current(DC) to alternating current (AC) inverter. Attached to each panel 152are a transmitter 402 and a receiver 408. The transmitter 402 andreceiver 408 may share common components and may be unified into atransceiver. A central control unit 410 is operatively attached to atransmitter 402 and a receiver 408 via load 150. Control unit 706 may beoperatively attached to transmitter 402 and a receiver 408 via powerline communications or via a wireless connection. Receiver 408optionally receives a signal from transmitter 402.

Reference is now made to FIG. 4d which shows a method 421 for theftdetection/prevention according to an embodiment of the presentinvention. Receiver 408 measures the signal strength (step 423) oftransmitters 402 within in the immediate vicinity of panel 152. A changein signal strength measured in the immediate vicinity of panel 152according to a predetermined threshold (step 425) is used to detect(step 427) an object in the immediate vicinity of panel 152. The changein signal strength detected by receiver 408 is conveyed to centralcontroller 410 which provides an alert of a potential theft of panel 152(step 429). If there is no significant change in threshold signalstrength (step 425) receiver 408 continues to measures the signalstrength (step 423) of transmitters 402 within in the immediate vicinityof panel 152.

Electric Field Strength Measurement

The term “electric field” as used herein refers to the electric fluxpresent in the space surrounding an electric charge or the electric fluxpresent in the space of a time-varying magnetic field. The spacesurrounding an electric charge or the space in the presence of atime-varying magnetic field may be air and/or a dielectric material. Theelectric field exerts a force on other electrically charged objects withthe magnitude of the force dependant on the inverse square relationshipof the distance between electrically charged objects.

Reference is now made to FIG. 5a which shows a power generation system501 including a theft prevention feature according to an embodiment ofthe present invention. Multiple photovoltaic panels 152 are connected inseries to form a string. The string of photovoltaic panels 152 areconnected across a load 150. Load 150 is preferably a direct current(DC) to alternating current (AC) inverter. Operatively attached to eachpanel 152 is a field sensor 502. Field sensor 502 typically measures theelectric field within panel 152 or in the electric field in theimmediate vicinity of panel 152. Attached to sensors 502 is a controller504 which is also attached to load 150.

Reference is now made to FIG. 5b which shows a typical cross section 590of photovoltaic panel 152. Cross section 590 shows typical parts 520 a,520 b, 522, 524 a, 534 b, 526 and 528 which may be included in aphotovoltaic panel 152. Parts 522, 524 a, 534 b, 526 and 528 are locatedin a casing 520 formed by parts 520 a (typically a metal alloy) and 520b (typically a metal alloy or a plastic type of material) is used tohouse an insulating sheet 522. Next to insulating sheet 522 is areactive encapsulant sheet 524 a which is typically made from ethylenevinyl acetate polymer. Next to reactive encapsulant sheet 524 a isphotovoltaic substrate 526 followed by another reactive encapsulantsheet 524 b. Finally after reactive encapsulant sheet 524 b is a sheettypically of low iron flat glass 528. The side of photovoltaic substrate526 adjacent to reactive encapsulant sheet 524 b is where the metaltracks 550 (not shown) are which connect electrically the photovoltaiccells 552 (not shown) of photovoltaic substrate 526. Sensor 502 may beplaced between photovoltaic substrate 526 and reactive encapsulant sheet524 a or in area A.

Reference is now made to FIG. 5c which shows a plan view photovoltaicpanel 152. The plan view shows casing 520 and photovoltaic cells 552with tracks 550 showing through transparent glass 528 and sheet 524 b.

Reference is now also made to FIG. 5d which shows an equivalentcapacitor 505 representing photovoltaic panel 152. Plate 530 and node Dequivalently represent the casing 520 of panel 152. Dielectric 534represents collectively; insulating sheet 522, reactive encapsulantsheets 524 b/524 a, photovoltaic substrate 526, low iron flat glass 528and the air space shown by area A in FIG. 5b . Plates 532 with node Erepresent the metal track deposit 550 which connects electrically thephotovoltaic cells 552 shown in FIG. 5c of photovoltaic substrate 526.The capacitance (C) in farads of capacitor 505 is given by equation Eq.1:

$\begin{matrix}{C = \frac{ɛ_{0}ɛ_{r}X}{d}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$with ε_(o)=permittivity of free space=8.85×10⁻¹² farads per meter,ε_(r)=relative permittivity or dielectric constant of dielectric 534,X=the area of plates 530 and 532 and d=the distance between plates 530and 532. An object in the vicinity of area A causes the dielectricconstant (ε_(r)) to vary since the air space shown by area A in FIG. 5bmakes up part of the dielectric constant (ε_(r)), hence the capacitance(C) varies and hence the electric field (E) varies in capacitor 505.

Reference is now also made to FIG. 5e which shows a method 511 for theftdetection/prevention according to an embodiment of the present inventionusing equivalent capacitor 505. Sensor 502 measures the electric fieldstrength (step 503) within panel 152 or in the electric field in theimmediate vicinity of panel 152 i.e. area A. A change in the electricfield strength measured field in the immediate vicinity of panel 152 orin panel 152 according to a predetermined threshold (step 505) is usedto detect (step 507) an object in the immediate vicinity of panel 152.The change in electric field strength detected by sensor 502 is conveyedto central controller 504 which provides an alert of a potential theftof panel 152 (step 509). If there is no significant change in thresholdof electric field strength (step 505) sensor 502 continues to measuresthe electric field strength (step 503).

Reflectometry from within a String

Reference is now made to FIG. 6a which shows a power generation system601 including a theft prevention feature according to an embodiment ofthe present invention. Multiple photovoltaic modules 606 are connectedin series to form a photovoltaic string 608. Photovoltaic string 608 isconnected across a load 150 via direct current (DC) power lines 610.Load 150 is preferably a direct current (DC) to alternating current (AC)inverter. Photovoltaic modules 606 have a photovoltaic panel 152 whichis operatively attached to switch unit 602. A central control unit 604is operatively attached to load 150 and typically provides a controlsignal and a test signal which are superimposed onto power lines 610 viaload 150. Switch unit 602 optionally receives the control signal fromunit 604 and in response to the control signal from unit 604; switchunit 602 typically reconfigures the connection of panel 152 to load 150by adding a resonant circuit in either series or parallel with panel152.

Reference is now made to FIG. 6b which shows further details ofphotovoltaic module 606 according to an embodiment of the presentinvention. Photovoltaic module 606 typically has switch unit 602connected across in parallel with a panel 152, in series with a stringof panels or switch unit 602 may be connected across a string of panels152. Multiple switch units may be activated independently. Switch unit602 is operatively attached to controller 604 and when switch unit 602connected in parallel with module 606, switch unit 602 preferably has aswitch S₁ connected in series with a capacitor C_(s) and inductor L_(s).Switch S₁ is activated by actuator 612 with actuator 612 deriving powerfrom connection across panel 152 as well as the control signal fromcentral control unit 604 to close switch S₁. The power that actuator 612derives from panel 152 additionally charges a storage device such as abattery located in actuator 612 to allow for nighttime operation ofswitch unit 602. Multiple switch units 602 may be activated/de-activatedindependently.

FIG. 6b shows that the resonant circuit is connected in parallel topanel 152. Alternatively, the resonant circuit may be in series to panel152 (with the resonance circuit being a parallel LC instead of a seriesLC).

The need for switching the resonance circuit is not mandatory and mightbe not available if actuator 612 does not have power for doing so.Reflectometry may be measured even if the resonance circuit is alwaysconnected (either in series or in parallel). However, the reason foradding this resonance switching is in order to command each string toeither activate or not activate the resonance. That way, we can control(via central unit, e.g load 150 in this case) which strings participatein the reflectometry measurement. Specifically, we would prefer to haveonly one string participating at a time which will enable us to get goodaccuracy for the measurement (meaning that all the other strings willhave their resonance switched off).

Reference is now made to FIG. 6c which shows a method 611 for theftdetection/prevention using system 601 according to an embodiment of thepresent invention. A control signal is superimposed onto power lines 610by controller 604 (step 603). The control signal superimposed onto powerlines 610 by controller 604 causes switch S₁ to close in switch unit602. Switch S₁ in closing switch unit 602 cause series resonant circuitcapacitor C_(s) and inductor L_(s) to be connected across panel 152(step 605). Typically switch S₁ closes for a predetermined time period.With S₁ closed a test signal is superimposed onto power lines 610 bycontroller 604 (step 607). The test signal controller 604 superimposesonto power lines 610 may be a time division reflectometry (TDR) signalor a frequency division reflectometry signal (FDR). The test signalpreferably resonates with series capacitor C_(s) and inductor L_(s).Series capacitor C_(s) and inductor L_(s) have values chosen to give anarrow band circuit of typically 15-25 MHz. Controller 604 then senses(step 609) the reflected TDR or FDR signal on power lines 610. If achange in sense threshold of reflected test signal is detected (step611) an alerting of potential theft may be made (step 613) otherwisetheft detection continues again with step 603.

Mesh Network

Reference is now made to FIG. 7a which shows a power generation system701 including a theft prevention feature according to an embodiment ofthe present invention. Multiple photovoltaic panels 152 are connected inseries to form a string. The string of photovoltaic panels 152 areconnected across a load 150. Multiple strings are then also connected inparallel. Load 150 is preferably a direct current (DC) to alternatingcurrent (AC) inverter. Attached to each panel 152 is an electronicmodule 702. Module 702 typically receives a data signal from controller704 via wireless or power line communications. For example, the datasignal that panel module B receives from controller 704 typicallyrequests panel module B to provide details of other panel modules in theimmediate vicinity of panel module B. The panel modules in the immediatevicinity of panel B are panel modules A, C and D. A panel moduletypically collects data of other panel modules in the immediate vicinityand sends a data signal back to controller 704 via wirelesscommunication or through the power lines connecting panels 152 to load150.

Reference is now made to FIG. 7b which shows a method 731 for theftdetection/prevention according to an embodiment of the presentinvention. Typically at the installation or upgrade of power generationsystem 701, details of system 701 in terms of electrical connectionand/or topological layout of panels 152 in system 701 is programmed in alook up table in controller 704. Using panel module B as an exemplaryembodiment of the present invention, controller 704 typically sends(step 703) a signal to panel module B via wireless communication orthrough the power lines connecting panels 152 to load 150. The signalsent from controller 704 to panel module B causes panel module B toconstruct a confirmation signal based on the signal sent from controller704 (step 705). The constructed confirmation typically includesinformation about panel module B and according to a feature of thepresent invention, information that panel module B collects from panelmodules A, C and D which are in the immediate vicinity of panel moduleB. Panel module B transmits the confirmation signal via wirelesscommunication or through the power lines connecting panels 152 to load150 where the confirmation signal is received by controller 704 (step707). Controller 704 then compares the received confirmation signal withthe look up table stored in controller 704 (step 709). If the comparisonis good (step 711), theft detection continues by sending a signal fromcentral controller 704 (step 703) otherwise a potential alert of theftof a panel and/or panels 152 is made (step 713).

Alternatively, probe signal (step 703) and confirmation signal (step705) may not be required. Instead, each module 702 may be programmed tosend a message periodically towards its neighbors, every three minutesfor instance. The message when received is first of all a message thatsays transmitting module 702 is alive and can also measure data, e.gimpedance and transmit data. The transmitted message is received byneighboring modules 702 and the transmission propagates along the meshnetwork until the transmission reaches controller 704 typically at thesite of the load/inverter/main-receiver.

It is to be understood that although there are described hereindifferent embodiments, the features of the various embodiments could becombined together, in any combination preferred by the skilled person.So doing can, for instance, provide a system with two or more theftprevention/detection devices and/or methods.

The definite articles “a”, “an” is used herein, such as “a converter”,“a switch” have the meaning of “one or more” that is “one or moreconverters” or “one or more switches”.

Examples of various features/aspects/components/operations have beenprovided to facilitate understanding of the disclosed embodiments of thepresent invention. In addition, various preferences have been discussedto facilitate understanding of the disclosed embodiments of the presentinvention. It is to be understood that all examples and preferencesdisclosed herein are intended to be non-limiting.

Although selected embodiments of the present invention have been shownand described individually, it is to be understood that at least aspectsof the described embodiments may be combined.

Also although selected embodiments of the present invention have beenshown and described, it is to be understood the present invention is notlimited to the described embodiments. Instead, it is to be appreciatedthat changes may be made to these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined bythe claims and the equivalents thereof.

The invention claimed is:
 1. A method comprising: receiving a pluralityof values, wherein a first value of the plurality of values correspondsto a measurement of an impedance of a photovoltaic direct current (DC)power source; retrieving a second value from a memory of a deviceassociated with a load; comparing the first value with the second valueto produce a comparison result; and alerting, by the device, a potentialtheft corresponding to the photovoltaic DC power source based on one of(i) the comparison result or (ii) determining that at least one value ofthe plurality of values does not correspond to an impedance measurement.2. The method according to claim 1, wherein said second value comprisesa hash of said first value.
 3. The method according to claim 1, furthercomprising: determining that the first value corresponds to the secondvalue; and enabling power conversion of an inverter of the load based onthe determination that the first value corresponds to the second value.4. The method according to claim 1, wherein the first value or thesecond value is generated by a global positioning system module whichbases at least a portion of one of the first value or the second valueon global coordinates of the photovoltaic DC power source or an inverterof the load.
 5. The method according to claim 1, further comprising:receiving a third value from a server associated with the load; andcomparing the third value with the second value to produce thecomparison result.
 6. The method according to claim 1, wherein at leasta portion of the first value or the second value is based on globalcoordinates of at least one of the photovoltaic DC power source or theload.
 7. The method according to claim 1, further comprising determiningthat the first value corresponds to the second value; transferring,based on the determining that the first value corresponds to the secondvalue, via a DC power line, electrical power output from thephotovoltaic DC power source to the load; and enabling electrical poweroutput of the load.
 8. The method according to claim 1, furthercomprising disabling, based on the comparison result, electrical powerconversion of an inverter of the load.
 9. The method according to claim1, further comprising determining that the first value does notcorrespond to the second value; and disabling, based on the determiningthat the first value does not correspond to the second value, electricalpower output of the load.
 10. A system comprising: a photovoltaic directcurrent (DC) power source configured to generate DC power andcomprising: a processor configured to calculate a plurality of values,wherein a first value of the plurality of values corresponds to ameasurement of an impedance of the photovoltaic DC power source; a firstmemory configured to store the first value; a load coupled to thephotovoltaic DC power source via a DC power line; a second memoryassociated with the load, the second memory configured to store a secondvalue; and a processor configured to receive the plurality of valuesfrom the photovoltaic DC power source, compare the first value of theplurality of values with the second value to produce a comparisonresult, and to alert a potential theft corresponding to the photovoltaicDC power source based on one of (i) the comparison result or (ii) adetermination, by the processor, that at least one value of theplurality of values does not correspond to a measurement of animpedance.
 11. The system according to claim 10, further comprising aglobal position module located at a location of the load or a locationof the photovoltaic DC power source, wherein at least a portion of oneof the first value or the second value is based on global coordinatesgenerated by the global position module.
 12. The system according toclaim 10, wherein said second value comprises a hash of said firstvalue.
 13. The system according to claim 10, wherein the processor isconfigured to determine that the first value corresponds to the secondvalue and to enable, based on a determination that the first valuecorresponds to the second value, power conversion of an inverter of theload.
 14. The system according to claim 10, wherein the first value orthe second value is generated by a global positioning system modulewhich bases at least a portion of the first value or the second value onglobal coordinates of the photovoltaic DC power source or an inverter ofthe load.
 15. The system according to claim 10, wherein the processor isconfigured to enable, based on a determination that the first valuecorresponds to the second value, electrical power output of the load.16. The system according to claim 10, further comprising: a servercomprising a third memory configured to store a third value, wherein theprocessor is further configured to compare at least one of the firstvalue and the second value to the third value to generate the comparisonresult.
 17. The system according to claim 10, wherein the photovoltaicDC power source comprises a second processor configured to: receive thesecond value; compare the second value with the first value to produce asecond comparison result; and alert a potential theft corresponding tothe photovoltaic DC power source based on the second comparison result.18. The system according to claim 17, wherein the photovoltaic DC powersource comprises a bypass, and wherein the second processor isconfigured to control the bypass to switch, based on the secondcomparison result, power generation by the photovoltaic DC power sourcefrom being disabled to being enabled or from being enabled to beingdisabled.
 19. An apparatus comprising: one or more processors; andmemory storing instructions that, when executed by the one or moreprocessors, cause the apparatus to: receive a plurality of values from aphotovoltaic direct current (DC) power source; calculate a first valueof the plurality of values, wherein the first value corresponds to ameasurement of an impedance of the photovoltaic DC power source;retrieve a second value from the memory, wherein the memory isassociated with a load; compare the first value with the second value toproduce a comparison result; and alert a potential theft correspondingto the photovoltaic DC power source based on one of (i) the comparisonresult or (ii) a determination, by the apparatus, that at least onevalue of the plurality of values does not correspond to a measurement ofan impedance.
 20. The apparatus according to claim 19, wherein theinstructions, when executed by the one or more processors, cause theapparatus to: receive a third value from a server associated with theload; and compare the third value with the second value to produce thecomparison result.
 21. The apparatus according to claim 19, wherein, theinstructions, when executed by the one or more processors, cause theapparatus to: determine that the first value corresponds to the secondvalue; and enable power conversion of an inverter of the load based onthe determination that the first value corresponds to the second value.